1. Field of the Invention
The present invention relates to apparatuses for measuring smooth and continuous shapes of a mold, a mirror, a lens, etc. of a relatively large aperture for use with a camera, a video, and a semiconductor manufacturing apparatus, etc., and more particularly to a shape measuring apparatus using multiple probes to measure aspheric shapes, spherical and plane three-dimensional shapes of a large aperture, which are hard to be measured by a normal interferometer.
2. Description of the Related Art
Conventional three-dimensional shape measuring apparatuses have typically scanned, in X-Y or r-xcex8 directions, a single probe which is able to measure a position in a Z direction, so as to measure a entire shape of an object to be measured.
Japanese Laid-Open Patent Publication No. 3-255907 discloses, as a typical example, a measuring apparatus which includes a single probe unit, mounted on a mechanism for scanning an object in X and Y directions, and obtains data relating to a surface shape of the object by measuring probe""s X, Y and Z positions when the probe traces the surface of the object.
However, the three-dimensional shape measuring apparatus in Japanese Laid-Open Patent Publication No. 3-255907 uses the single probe to scan the surface of the object, disadvantageously requiring time to measure the entire surface of the object.
An arrangement of a plurality of probes is one conceivable a solution for this problem. Japanese Laid-Open Patent Publication No. 6-317412 discloses a plurality of probes arranged in a row on a vertically and horizontally movable frame so as to scan a relief shape of an object by moving the movable frame.
Recent lenses, mirrors, molds, etc. have increasingly required a smooth and continuous surface shape with an extremely strict surface precision such as 0.1 xcexcm or below. Therefore, an acquisition of precise three-dimensional shape data requires an accurate recognition of a position in a Z-axis direction as well as positions in X-axis and Y-axis directions.
Accordingly, it is an exemplary object of the present invention to provide an apparatus and method for measuring a shape using a multiple probes, which may provide precise three-dimensional data of an object to be measured, and eliminate the above disadvantages.
In order to achieve the above object, a shape measuring apparatus of one aspect of the present invention, which defines an XYZ-axis coordinate and measures a surface shape of an object includes a plurality of probes arranged in a Y-axis direction, the probes contacting a surface of the object, and moving in a Z-axis direction according to the surface shape of the object, a probe holder for holding each of the plurality of probes movable in the Z-axis direction, a moving mechanism for moving the probe holding mechanism in an X-axis direction relative to the object, first and second measuring instruments for measuring positions of each probe in the X-axis and Y-axis directions, a third measuring instrument for measuring a position of each probe in the Z-axis direction, and a computing unit for calculating the surface shape of the object based on measuring results from the first, second, and third measuring instruments. In an alternative aspect of the present invention, the first and second measuring instruments measure moving amounts of each probe in the X-axis and Y-axis directions.
The first and second measuring instruments may additionally measure inclinations of each probe in rotating directions around the X-axis and Y-axis, so as to correct the surface shape of the object calculated by the computing unit. The first and second measuring instruments may measure the inclinations of each probe in the rotating directions around the X-axis and Y-axis by measuring a plurality of points of the probes in the Z-axis direction. A plurality of first and second measuring instruments may be respectively arranged in the Z-axis direction, and simultaneously measure the plurality of points in the Z-axis direction.
The probe holder may hold the probes using a non-contact air guide that allows the probes to be movable only in the Z-axis direction, and each probe may be connected to a cylinder mechanism for adjusting a contact force between the probe and the object by balancing probe""s own weight.
The moving mechanism may move the probe holder in the X-axis direction while allowing the probes to contact the surface of the object.
The moving mechanism may move the probe holder in the X-axis direction while the probe is being separated from the surface of the object after measurements by the first, second and third measuring instruments.
The shape measuring apparatus may further include a second moving mechanism for moving the probe holder in the Y-axis direction relative to the object.
The probe may include a first position-measuring plane mirror arranged and rotated by a first angle from the X-axis around the Z-axis, and a second position-measuring plane mirror arranged and rotated by a second angle from the Y-axis around the Z-axis, wherein the first measuring instrument may include a first reference plane mirror arranged and rotated by the first angle from the X-axis around the Z-axis, and measure a separation between the first position-measuring plane mirror and the first reference plane mirror, and wherein the second measuring instrument may include a second reference plane mirror arranged and rotated by the second angle from the X-axis around the Z-axis, and measure a separation between the second position-measuring plane mirror and the second reference plane mirror. The first and second angles may be about 45xc2x0.
Each probe may include a third position-measuring plane mirror for measuring a position of the probe in the Z-axis, wherein the third measuring instrument may include a third reference plane mirror having a normal in the Z-axis direction, and measure a separation between the third position-measuring plane mirror and the third reference plane mirror. The probe may include a position-measuring mirror block provided with the first and second position-measuring plane mirrors, a contact ball that is attached to a tip of the position-measuring mirror block, and contacts the object, and a probe shaft provided at a rear end of the position-measuring mirror block, the third reference plane mirror being formed at a rear end surface of the position-measuring mirror block. The probe shaft has a hollow part, through which the third measuring instrument measures the separation between the third position-measuring plane mirror and the third reference plane mirror.
A shape measuring method of another aspect of the present invention for measuring a surface shape of an object on an XYZ-axis coordinate includes the steps of moving, in a Z-axis direction, a plurality of probes arranged in a Y-axis direction, while bringing each probe into contact with the object, measuring contact position between each probe and the object in X-axis and Y-axis directions using first and second measuring instruments, measuring a contact position of each probe in the Z-axis direction using a third measuring instrument, moving the plurality of probes in the X-axis direction relative to the object, repetitively measuring contact positions of each probe in the X-axis, Y-axis, and Z-axis directions using the first, second and third measuring instruments, and calculating the surface shape of the object based on contact positions in the X-axis, Y-axis, and Z-axis directions measured by the first, second and third measuring instruments.
A shape measuring method of still another aspect of the present invention for measuring a surface shape of an object on an XYZ-axis coordinate includes the steps of moving, in a Z-axis direction, a plurality of probes arranged in a Y-axis direction, while bringing each probe into contact with the object, measuring contact positions between each probe and the object in X-axis and Y-axis directions using first and second measuring instruments, measuring the contact position in the Z-axis direction using a third measuring instrument, measuring one sectional shape of the object in the Y-axis direction from the contact positions of the plurality of probes measured by the first, second and third measuring instruments, moving the plurality of probes in the X-axis direction relative to the object, repetitively measuring a plurality of sectional shapes in the Y-axis directions using the first, second and third measuring instruments, and calculating the surface shape of the object using the plurality of sectional shapes in the Y-axis direction measured by the first, second and third measuring instruments.
The above and other objects of the present invention will become more apparent from the following drawings taken in conjunction with the accompanying drawings.